1 #ifndef _URCU_QSBR_STATIC_H
2 #define _URCU_QSBR_STATIC_H
7 * Userspace RCU QSBR header.
9 * TO BE INCLUDED ONLY IN CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU
10 * RELEASE. See urcu.h for linking dynamically with the userspace rcu library.
12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
13 * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
15 * This library is free software; you can redistribute it and/or
16 * modify it under the terms of the GNU Lesser General Public
17 * License as published by the Free Software Foundation; either
18 * version 2.1 of the License, or (at your option) any later version.
20 * This library is distributed in the hope that it will be useful,
21 * but WITHOUT ANY WARRANTY; without even the implied warranty of
22 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
23 * Lesser General Public License for more details.
25 * You should have received a copy of the GNU Lesser General Public
26 * License along with this library; if not, write to the Free Software
27 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
29 * IBM's contributions to this file may be relicensed under LGPLv2 or later.
39 #include <urcu/compiler.h>
40 #include <urcu/arch.h>
41 #include <urcu/system.h>
42 #include <urcu/uatomic.h>
43 #include <urcu/list.h>
44 #include <urcu/futex.h>
45 #include <urcu/tls-compat.h>
52 * This code section can only be included in LGPL 2.1 compatible source code.
53 * See below for the function call wrappers which can be used in code meant to
54 * be only linked with the Userspace RCU library. This comes with a small
55 * performance degradation on the read-side due to the added function calls.
56 * This is required to permit relinking with newer versions of the library.
60 #define rcu_assert(args...) assert(args)
62 #define rcu_assert(args...)
66 RCU_READER_ACTIVE_CURRENT
,
67 RCU_READER_ACTIVE_OLD
,
71 #define RCU_GP_ONLINE (1UL << 0)
72 #define RCU_GP_CTR (1UL << 1)
76 * Global quiescent period counter with low-order bits unused.
77 * Using a int rather than a char to eliminate false register
78 * dependencies causing stalls on some architectures.
83 } __attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
85 extern struct rcu_gp rcu_gp
;
88 /* Data used by both reader and synchronize_rcu() */
90 /* Data used for registry */
91 struct cds_list_head node
__attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
96 extern DECLARE_URCU_TLS(struct rcu_reader
, rcu_reader
);
99 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
101 static inline void wake_up_gp(void)
103 if (caa_unlikely(_CMM_LOAD_SHARED(URCU_TLS(rcu_reader
).waiting
))) {
104 _CMM_STORE_SHARED(URCU_TLS(rcu_reader
).waiting
, 0);
106 if (uatomic_read(&rcu_gp
.futex
) != -1)
108 uatomic_set(&rcu_gp
.futex
, 0);
110 * Ignoring return value until we can make this function
111 * return something (because urcu_die() is not publicly
114 (void) futex_noasync(&rcu_gp
.futex
, FUTEX_WAKE
, 1,
119 static inline enum rcu_state
rcu_reader_state(unsigned long *ctr
)
123 v
= CMM_LOAD_SHARED(*ctr
);
125 return RCU_READER_INACTIVE
;
127 return RCU_READER_ACTIVE_CURRENT
;
128 return RCU_READER_ACTIVE_OLD
;
132 * Enter an RCU read-side critical section.
134 * This function is less than 10 lines long. The intent is that this
135 * function meets the 10-line criterion for LGPL, allowing this function
136 * to be invoked directly from non-LGPL code.
138 static inline void _rcu_read_lock(void)
140 rcu_assert(URCU_TLS(rcu_reader
).ctr
);
144 * Exit an RCU read-side critical section.
146 * This function is less than 10 lines long. The intent is that this
147 * function meets the 10-line criterion for LGPL, allowing this function
148 * to be invoked directly from non-LGPL code.
150 static inline void _rcu_read_unlock(void)
155 * Returns whether within a RCU read-side critical section.
157 * This function is less than 10 lines long. The intent is that this
158 * function meets the 10-line criterion for LGPL, allowing this function
159 * to be invoked directly from non-LGPL code.
161 static inline int _rcu_read_ongoing(void)
163 return URCU_TLS(rcu_reader
).ctr
;
167 * This is a helper function for _rcu_quiescent_state().
168 * The first cmm_smp_mb() ensures memory accesses in the prior read-side
169 * critical sections are not reordered with store to
170 * URCU_TLS(rcu_reader).ctr, and ensures that mutexes held within an
171 * offline section that would happen to end with this
172 * rcu_quiescent_state() call are not reordered with
173 * store to URCU_TLS(rcu_reader).ctr.
175 static inline void _rcu_quiescent_state_update_and_wakeup(unsigned long gp_ctr
)
178 _CMM_STORE_SHARED(URCU_TLS(rcu_reader
).ctr
, gp_ctr
);
179 cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */
185 * Inform RCU of a quiescent state.
187 * This function is less than 10 lines long. The intent is that this
188 * function meets the 10-line criterion for LGPL, allowing this function
189 * to be invoked directly from non-LGPL code.
191 * We skip the memory barriers and gp store if our local ctr already
192 * matches the global rcu_gp.ctr value: this is OK because a prior
193 * _rcu_quiescent_state() or _rcu_thread_online() already updated it
194 * within our thread, so we have no quiescent state to report.
196 static inline void _rcu_quiescent_state(void)
198 unsigned long gp_ctr
;
200 if ((gp_ctr
= CMM_LOAD_SHARED(rcu_gp
.ctr
)) == URCU_TLS(rcu_reader
).ctr
)
202 _rcu_quiescent_state_update_and_wakeup(gp_ctr
);
206 * Take a thread offline, prohibiting it from entering further RCU
207 * read-side critical sections.
209 * This function is less than 10 lines long. The intent is that this
210 * function meets the 10-line criterion for LGPL, allowing this function
211 * to be invoked directly from non-LGPL code.
213 static inline void _rcu_thread_offline(void)
216 CMM_STORE_SHARED(URCU_TLS(rcu_reader
).ctr
, 0);
217 cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */
219 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
223 * Bring a thread online, allowing it to once again enter RCU
224 * read-side critical sections.
226 * This function is less than 10 lines long. The intent is that this
227 * function meets the 10-line criterion for LGPL, allowing this function
228 * to be invoked directly from non-LGPL code.
230 static inline void _rcu_thread_online(void)
232 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
233 _CMM_STORE_SHARED(URCU_TLS(rcu_reader
).ctr
, CMM_LOAD_SHARED(rcu_gp
.ctr
));
241 #endif /* _URCU_QSBR_STATIC_H */